1. Field of the Invention
This invention relates to binary measuring, counting, and recording systems, and more particularly to such systems using binary notation to express numerical data with a small number of bits for each piece of numerical information involved.
2. Description of the Prior Art
Of the many codes that exist in today's digital electronic world, only two major techniques are generally accepted. These are pulse code modulation and delta modulation. PCM systems output a digital data word for each measurement increment which entirely defines the position of that increment. Measurement granularity is determined by the number of digital bits or length of data word allocated for a given data or voltage excursion. Delta modulated systems utilize only one bit and provide only incremental changes. There are many situations where this type data coding is very useful and practical. These are the only two "pure" fundamental approaches to digital coding; however, a large percentage of applications exist where neither of these provide an acceptable solution.
One classic, nonelectronic example of this shortcoming is the standard carpenter's ruler. The smallest increment or graduation on the ruler is one-sixteenth of an inch denoted by evenly spaced lines. On most, different lengths of lines denote various fractions of inches. The inch marks are numbered corresponding to relative position as are the foot or 12 inch increments. Most persons find no difficulty in making measurements with this type system of measure; not so electronically. If this ruler were graduated in delta modulation, which might be the only feasible marking system if, for instance, the ruler had the width of a pencil, none of the graduations would be numbered and all lines would be the same length. In order to make a measurement each line would have to be counted from one end or the other to the measured point. With PCM, each graduation would have to be numbered in 16ths. Clearly, this is not possible for reasons of utility on most rulers. In other words, the ruler uses a code of its own in order to accomplish its goal which it would not do through the use of PCM or delta modulation, and the simplicity of the code and its obvious utility are attested to by the longevity of this method.